1. Field of the Invention
The present invention relates to a load cell attachment structure.
Priority is claimed on Japanese Patent Application No. 2004-259502, filed Sep. 7, 2004, and on Japanese Patent Application No. 2004-259503, filed Sep. 7, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In order to control operating and the like of an air bag system when a collision of a vehicle happens, a load cell which measures load acting on a seat is mounted on the vehicle. Then, it is determined whether an occupant is seated or not, and whether the occupant who is seated is an adult or a child, and the like.
For example, there is a system which includes stud bolts projecting above, which is disposed on the front and rear of sliders of bilateral seat rails, a plate member which is fixed on the stud bolts and a seat frame. One end of the plate member is fixed on a tip of the stud bolts which go through holes of the seat frame, and the other end of the plate member is fixed on the seat frame (refer to U.S. Pat. No. 6,161,891). In the reference, amount of deformation of the plate member is measured.
Also, as shown in FIG. 7, there is a system in which a male screw 102 is disposed on a load sensing part 101 of a load cell 100, the load cell 100 is attached to a slider 103 of a seat rail facing upward toward the load sensing part 101, and an attachment plate 104 of a seat frame is attached to the load cell 100 by engaging a nut 105 with the male screw 102. In this system, when the attachment plate 104 is attached to the load sensing part 101 by fastening the nut 105 to the male screw 102 tightly, if only the attachment plate 104 of the seat frame warps or inclines slightly due to a minor accident of the vehicle or the like, the load cell 100 measures slight loads are caused by the warp or the incline. As a result, the load cell 100 cannot measure loads accurately. Accordingly, as shown in FIG. 8, it is proposed that clearance which allows warp or the incline of the attachment plate 104 be formed between the nut 105 and the load sensing part 101 by disposing a collar 106 between the nut 105 and the load sensing part 101. However, in this system, a fastening force along the longitudinal direction of the male screw 102 acts on the load sensing part 101 through the collar 106. As a result, the load cell 100 senses undesired load. In other words, drift force along the axis is caused on the load cell 100.